Take ashtanga yoga as a start: a discipline that combines stretching, strength training, and meditative breathing. And then add some extra special poses (also known as postures or their Sanskrit name, asanas) which are rooted in calisthenics. This means push-ups and handstands, toe touches and side bends.
There is one more big difference between Ashtanga yoga and Power yoga: the pace and rhythm. Instead of pausing between poses as you would in traditional yoga, each move flows into the next, making it an intense aerobic workout. This explains why you will sweat a lot and build your muscles.